Crease, Robert P. (2011). World in the Balance: the historic quest for an absolute system of measurement. New York: W.W. Norton. p. 317. ISBN978-0-393-07298-3.

di Francia, Giuliano Toraldo (1976). The Investigation of the Physical World. Cambridge: Cambridge University Press. ISBN0-521-29925-X Originally published in Italian as L'Indagine del Mondo Fisico by Giulio Einaudi editore 1976; first published in English by Cambridge University Press 1981.